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    <title>Document</title>
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    <script>
        // 声明变量
        let a;
        let b,c,d;
        let e = 100;
        let f = 521,g = 'iloveyou',h = [];

        // 1、变量不能重复声明
        // let star = '王嘉尔';
        // let star = '周星驰';

        // 2、块级作用域  全局，函数，eval
        // if else while for
        // {
        //     let girl = '刘雯';
        // }
        // console.log(girl);

        // 3、不存在变量提升
        // console.log(song);
        // let song = '尚硅谷';

        // 4、不影响作用域链
        {
            let school= '武工大';
            function fn(){
                console.log(school);
            }
            fn();
        }
    </script>
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